Throughout the preseason, we’ll take a look at the best – and worst – the NFL has to offer, unit by unit. Look for a new set of rankings every few days.

Imagine you’re a wide receiver going over the middle of a football field as the quarterback cocks his arm and throws a frozen rope into your midsection.

Then, out of the corner of your eye, you notice a quick flash of an opponent’s jersey before 250 pounds of linebacker crushes you like a fat man squeezes the final empty can of beer for the night.

Welcome to NFL. You’ve just been baptized by Brian Urlacher, Joey Porter and Ray Lewis. Don’t bother coming back to the middle; you’re not wanted.

Criteria for linebacker units:

The whole group, whether it is a three- or four-man unit, must have at least one run stuffer, one cover guy that could drop into coverage, and at least one teeth-rattling bone crusher that lays the hammer every Sunday.

The Top 10:

1. Pittsburgh SteelersJoey Porter, Larry Foote, James Farrior, Clark Haggans
The Super Bowl champs house the best linebacker core in the NFL based on speed, power and everything in between. Joey Porter can rush a passer or drop into coverage better than most LBs and James Farrior has been a force in the middle of this unit since coming over from the Jets in 2002. Many thought there would be a significant drop off from Kendrell Bell to Larry Foote, but the former Wolverine has been a sure tackler and steady performer. Clark Haggans isn’t as widely known as the other three, but he had his best season last year and produced nine sacks.

2. Chicago BearsBrian Urlacher, Lance Briggs, Hunter Hillenmeyer
After a one-year hiatus, Brian Urlacher returned to Hawaii last year for his fifth-career Pro Bowl appearance. Urlacher is possibly the most athletic linebacker in the league and has the speed to match his nasty hits. Lance Briggs had 170 tackles last year, which was one less than Urlacher, and he excels against the run. Hunter Hillenmeyer is a smart player that comes in on passing downs for Da Bears and shows great range when dropping into coverage.

3. San Diego ChargersShawne Merriman, Randall Godfrey, Steve Foley, Donnie Edwards
The Chargers have a nice blend of young and old in their unit and it’s highlighted by NFL Defensive Rookie of the Year Shawne Merriman. Merriman is the complete package and can play both the run and the pass, and, as his 10 rookie sacks demonstrate, he can drop the quarterback as well. Donnie Edwards and Randall Godfrey are very experienced; in fact, only Zach Thomas of the Dolphins has more tackles since 1999 than Edwards. Steve Foley struggled in the speed department last year because of a stomach injury, but he’s fit and ready to go again this year.

4. Tampa Bay BuccaneersDerrick Brooks, Shelton Quarles/Barrett Ruud, Ryan Nece
Try telling Derrick Brooks he’s losing a step and watch him take the breath right out of you as he lays out a quarterback. Brooks is still the centerpiece of Tampa’s defense even heading into his 12th season while Shelton Quarles had a career year battling with rookie Barrett Ruud. Ryan Nece stepped up nicely in his first go-round as a starter last year, and the addition of Jamie Winborn in the offseason will give this unit good depth in case of an injury.

5. Seattle SeahawksLofa Tatupu, Julian Peterson, LeRoy Hill
Watching Lofa Tatupu play last year, particularly in the Super Bowl, one would have sworn he was a veteran leader and not a rookie. Heading into only his second season, Tatupu commands a lot of respect from his teammates and will give Seattle a born leader for many years to come. The addition of Julian Peterson from San Francisco will be huge if he can rebound from injury. Peterson is a Pro Bowl player when healthy, and together with opposite outside linebacker LeRoy Hill (who was also a rookie last year), the Seahawks will have a nasty pass rush this season.

6. Denver BroncosIan Gold, D.J. Williams, Al Wilson
The Broncos are stacked at linebacker with three quality starters in Ian Gold, D.J. Williams and Al Wilson. Williams was excellent as a rookie two years ago, but took a bit of a step back last season. Wilson is an emotional leader who is smart and very productive. The defense revolves around Gold and his addition last year served an immediate impact. This unit doesn’t produce out-of-this-world numbers, but that’s mainly because they drop into coverage a lot and they all play the pass particularly well.

7. Buffalo BillsTakeo Spikes, London Fletcher, Angelo Crowell
This unit has tons of experience and plays extremely well together. Takeo Spikes is the glue that holds this core together and when he was lost for the season in Week 3 last year, the squad lost its leader and face. London Fletcher remains a consistent force in the middle and if the Bills could ever get a big tackle to take some heat off of him, Fletcher would dominate even more than he does now. Angelo Crowell played very well last year when Spikes went down with injury.

8. Miami DolphinsZach Thomas, Channing Crowder, Donnie Spragan
Zach Thomas made his sixth Pro Bowl appearance last year, the most ever by a Dolphins defender. After 10 season, Thomas still makes virtually every tackle on Miami’s D and nobody thought he would ever amount to much at 5-11, 228 pounds. Channing Crowder will be a Pro Bowl player sometime in his career, with the Dolphins hoping that he’s heading to Hawaii sooner rather than later. The steal of the third round and possibly the entire draft in 2005, Crowder flies to the football and is a born playmaker. Donnie Spragan plays a bit conservative, but never seems to play himself out of position and is very smart.

9. New York GiantsLaVar Arrington, Antonio Pierce, Carlos Emmons
If LaVar Arrington can reset his career in New York like the Giants think (or hope) he will, the G-Men will have a destructive linebacker force in ’06. Arrington is a great pas rusher and will be better because of former Redskins teammate Antonio Pierce. Pierce is a real student of the game and is the Giants’ quarterback on defense. Carlos Emmons needs to bounce back from injuries or else Brandon Short will have no problem stepping back into the starting lineup.

10. Baltimore RavensRay Lewis, Adalius Thomas, Bart Scott
The Ravens were easily ranked 10 spots up from where they are now only a few short years ago, but with Ray Lewis consistently falling to the injury bug over the past four years, this unit has dropped some. Lewis is said to be more motivated and quicker in preseason than he has been over the past couple of years, which should cause a fair deal of concern for any opposing running back. Adalius Thomas is the most versatile athlete in this unit and led the Raves in sacks (nine) and fumble recoveries (four) last season while Bart Scott was a pleasant surprise last year in his first crack at the starting lineup.

The Bottom Five:

28. San Francisco 49ersManny Lawson, Brandon Moore, Derek Smith, Jeff Ulbrich
Poor San Francisco; they keep getting picked on in these rankings, but it’s tough not to consider this group one of the worst in the league. Without Julian Peterson and with Jeff Ulbrich trying to bounce back from an injury shorted 2005, this unit is very inexperienced, but also shows promise with Manny Lawson getting a chance to start right away.

29. Minnesota VikingsE.J. Henderson, Ben Leber, Napoleon Harris
This unit was in trouble before drafting Chad Greenway in the first round this year, and they’re still in trouble after losing Greenway to a season-ending knee injury in the preseason opener. Ben Leber is trying to recover from a foot injury and E.J. Henderson isn’t that strong of a play caller in the middle. Napoleon Harris was a major disappointment last year since coming over from Oakland in the Randy Moss trade.

30. Houston TexansSam Cowart, Morlon Greenwood, Shantee Orr/DeMeco Ryans
Sam Cowart is aging, but still has plenty left in his tank to teach the promising Shantee Orr a thing or two about the position. Orr led the team in sacks last year and shows some athleticism, but he, Cowart and Morlon Greenwood will only be challenged by rookie DeMeco Ryans for their starting jobs.

31. New Orleans SaintsScott Fujita, Alfred Fincher, Tommy Polley
This unit was put together with a bunch of career backups or former hopefuls. Anthony Simmons decided to retire abruptly after arriving to camp and that left the unit even thinner than when he got to New Orleans. Scott Fujita was a solid signing, but he’s not spectacular and couldn’t hang with Kansas City and Dallas. The Saints really like Alfred Fincher, but he’s mostly played as a reserve or special teams player, while Tommy Polley never seemed to live up to the expectations he once had in St. Louis and Baltimore.

32. Oakland RaidersThomas Howard, Kirk Morrison, Sam Williams
The Raiders are probably going to struggle getting off the field this year on defense. Danny Clark is very susceptible in the passing game while Sam Williams missed all of last year after suffering an injury in camp. Kirk Morrison led all rookies with 116 tackles in ‘05 and may match or even top that number this year on a fast but inexperienced Oakland defense.